\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes,}
\begin{document}
\small
\begin{tikzpicture}[>=latex,scale=1]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw [->](-2,0)--(7,0)node[right]{$\omega t$};
  \draw [->](0,-1.5)--(0,1.5)node[right]{$i$};
  \draw [ultra thick] plot[domain=0:5.3, samples=1000] function{sin(x+1)} ;
  \draw [ultra thick, dashed] plot[domain=-1:0, samples=100] function{sin(x+1)};
  \node at (1,1) [above]{$i_1$};
  \draw [very thick] plot[domain=0:5.3+.5, samples=1000] function{.7*sin(x+.5)}node [above]{$i_2$} ;
  \draw [very thick, dashed] plot[domain=-.5:0, samples=100] function{.7*sin(x+.5)};
  \draw [dashed] (-1,0)--(-1,-1.5);\draw [dashed] (-.5,0)--(-.5,-1);
  \draw [<->] (0,-1.2)--node[below]{$\phi_1$}(-1, -1.2);
  \draw [<->] (0,-.65)--node[above]{$\phi_2$}(-.5,-.65);
  \draw [<->] (-1,-.75)--node[above]{$\Delta \phi$}(-.5,-.75);
\end{tikzpicture}
\end{document}